I9EI 
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THE  EFFECT  OF  ATMOSPHERIC  OXIDATION 

ON  THE 

LUBRICATING  PROPERTIES  OF  OILS 


JOHN  BREWSTER  HOFFMAN 


THESIS 


FOR  THE 


DEGREE  OF  BACHELOR  OF  SCIENCE 


in 


CHEMISTRY 


COLLEGE  OF  LIBERAL  ARTS  AND  SCIENCES 


UNIVERSITY  OF  ILLINOIS 


1921 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/effectofatmospheOOhoff 


/ 92  I 
H67 


UNIVERSITY  OF  ILLINOIS 

___J2ine._3.Oj 192JL 

THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 


ENTITLED, _ 

John  Brewster  Hoffman 
effect  of  Atmospherio  Oxidation  on  tho 

_ J02  P_§iliPi£  _ ?J:  P-£  ejrtie  s_  _o  £_  _0  i_l 

IS  APPROVED  BY  ME  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR  THE 
DEGREE  OF  


Approved  : 

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t Instructor  in  Charge 

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HEAD  OF  DEPARTMENT  OF  _ _ 

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500281 


THE  EFFECT  OF  ATMOSPHERIC  OXIDATION  ON  THE 


LUBRICATING  PHOPERTIES  OF  OILS. 

INTRODUCTION. 

It  is  a wall  known  fact  that  oils  in  use  deteriorate  in  their  lubricating 
power  considerably,  and  it  is  the  aim  of  this  problem  to  determine  how  much  of  this 
is  due  to  the  affect  of  atmospheric  oxidation,  and  what  are  the  possibilities  of 
nullifying  this  affect.  A catalytic  effect  due  to  metallic  particles  in  the  oil 
may  have  some  relation  to  the  changes  and  also  a method  for  reclaiming  the  oil  may 
be  suggested. 

To  be  truly  valuable  the  effects  of  the  exposure  should  be  related  to 
the  lubricating  power  as  determined  by  both  the  physical  and  chemical  tests  which 
have  been  found 'most  effective  for  this  purpose.  The  work  on  the  oil  should  also 
imitate  as  nearly  as  possible  the  conditions  affecting  it  in  use;  that  is,  the 
temperatures  should  be  those  commonly  found  in  bearings,  the  light  conditions 
should  be  those  usually  found  in  practice  and  the  gas  (air)  should  be  used  alone 
without  studying  the  effects  of  sulfur  dioxide,  carbon  dioxide,  hydrocarbon  gases, 
etc.  as  Conradson’haas  suggested  and  devised  his  apparatus  for.  Finally,  since  we 
wish  to  approximate  working  conditions  as  closely  as  possible,  the  oil  should  be 
subjected  to  some  mechanical  treatment. 

Because  of  the  fact  that  the  lubricating  problem  is  of  great  importance 
in  industry,  and  because  there  is  as  yet  neither  a general  knowledge  of  the  causes 
of  deterioration,  nor  a distinct  idea  of  the  changes  taking  place  in  the  oil  itself 
the  problem  has  been  undertaken.  The  work  was  carried  out  under  the  direction  of 
Dr.  W»  S.  Putnam,  to  whom  I wish  to  express  my  thanks  and  appreciation  for  his 


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very  constructive  criticism  and  helpful  suggestions  as  to  the  way  in  which  the 
problem  should  he  attacked. 

HISTORICAL. 

Previous  methods  of  studying  this  or  similar  effects  on  oils  made  use  of 

2 

apparatus  of  the  simplest  type.  C.  E.  Waters  simply  used  erlenmeyer  flasks,  con- 
taining each  about  ten  gms.  of  oil.  These  flasks  were  closed  by  filter  paper  (to 
exclude  dust)  and  placed  on  white  paper  on  a window  ledge  exposed  to  sunlight  and 
air.  Over  four  hundred  hours  of  exposure  was  undergone,  daily  tests  being  made 

on  the  oils  to  determine  the  change  in  weight,  loss  of  CO  and  HP0. 

2 ^ 

3 4 

galoziecki  in  1891  and  Hirsch  1894  tried  the  effect  of  blowing  air 

through  oil  in  the  cold  but  found  very  little  effect  was  produced  except  possibly 

5 

in  the  presence  of  sodium  hydroxide.  Arsinonann  confirmed  these  results.  In 

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1892,  Holde  exposed  samples  of  both  mineral  and  vegetable  oils  to  air  and  deter- 
mined the  changes  in  acidity,  unsaturation,  viscosity  and  specific  gravity.  Ha 

found  that  mineral  oils  suffered  practically  no  change  compared  to  vegetable  oils. 

7 

C.  E.  Waters  in  another  series  of  experiments  tried  the  effect  of  sim- 
ple heating  in  air.  The  carbonization  or  asphalt  residue  produced  was  the  prin- 
cipal factor  determined.  These  tests  seemed  to  show  that  simple  heating  out  of 

contact  with  air  produced  little  residue.  However,  in  his  work  previously  refer- 

o 

red  to,  the  oils  which  were  exposed  to  air  iTere  also  heated  to  250  and  the  rela- 
tive carbonization  noted,  in  these  tests  the  carbonization  according  to  waters' 
figures  proceeded  about  55  times  as  fast  with  heating,  indicating  that  the  effect 
producing  the  residue,  probably  polymerization,  largely  is  due  to  heat  to  an  even 
greater  extent  than  to  oxygen.  Though  the  presence  of  the  latter  seems  necessary, 


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the  majority  of  these  previous  investigations  were  conducted,  by  passing  air  or 
other  gas  over  the  surface  of  the  oil.  This  doubtless  produces  similar  results 
to  the  method  of  ’’blowing  through”  but  relatively  speaking  the  surface  layer  of 
the  oil  must  be  considered  as  over-oxidized  with  reference  to  the  rest  of  the  oil 
unless  mechanical  stirring  was  used.  At  a constant  temperature  there  would  be 
little  in  the  way  of  convection  currents,  and  practically  the  only  diffusion  of 
the  surface  layer  throughout  the  body  of  the  liquid,  and  the  only  means  of  pre- 
senting a new  surface  to  the  air  would  be  by  movement  due  to  a difference  in  spe- 
cific gravity  as  oxidation  progressed.  A very  slight  motion  might  also  occur 
through  friction  of  the  moving  gas  on  the  surface  of  the  oil. 

The  present  problem  tries  to  overcome  these  conditions,  giving  an 
action  on  the  oil  which  more  nearly  approximates  that  found  under  working  condi- 
tions. The  tests,  alsc^  are  made  with  the  prime  object  of  relating  the  changes 
in  the  oil  to  its  value  as  a lubricant,  which  practically  none  of  the  previous 
experiments  attempted. 

APPARATUS. 

The  apparatus  used  to  oxidize  the  oil  was  constructed  to  heat  the  oil, 
blow  air  through  it,  and  stir  it  vigorously  at  the  same  time.  A tall  beaker  (C, 
see  figure)  holding  700  cc.  of  oil  to  be  tested  was  placed  in  an  oil  bath  (D) 
consisting  of  a larger  beaker  containing  cotton  seed  oil.  These  rested  on  a ring 
stand  and  were  heated  by  a blast  lamp.  A hollow  vertical  shaft  (B)  revolved  by 
an  electric  motor  and  having  two  propellor  shaped  blades  (p)  at  the  lower  end 
was  placed  in  the  test  oil  in  the  inner  beaker,  inside  of  the  shaft  a station- 
ary glass  tube  (A)  was  held.  This  tube  extended  to  the  bottom  of  the  oil,  where 


OXIDIZING  APPARATUS 


CARBON  RESIDUE  APPARATUS 


4 

it  was  bant  at  right  angles  so  that  the  stream  of  air  blown  through  it  would  bub- 
ble through  the  oil.  In  order  to  make  the  conditions  with  regard  to  moisture  and 
amount  of  air  as  uniform  as  possible  the  tube  was  connected  to  a side  tube  ex- 
tending to  the  bottom  of  a water  column  about  a meter  high.  The  water  column  reg- 
ulated the  pressure,  as  long'  as  an  excess  of  air  was  passed  into  the  system,  by 
permitting  this  excess  to  escape  through  the  water,  the  pressure  thus  being  con- 
stant and  proportional  to  the  height  of  the  column.  Just  before  passing  into  the 
oil  the  air  was  dried  by  inserting  a CaCl^  tube  in  the  line. 

The  same  oil  was  used  throughout  the  tests,  it  being  a standard  auto- 
mobile lubricant  of  "medium”  body  from  Pennsylvania  crude. 

EXPERIMENTAL  (METHOD) . 

Two  test  runs  of  4 and  8 hours  respectively  at  60°  were  first  made  to 
determine  the  approximate  amount  of  change  which  might  be  expected.  Very  little 
change  was  noted  in  the  oil  from  these  so  the  final  runs  were  made  as  follows: 


Sample  Number 

Time  of  Run 

Temperature 

Catalyst 

II 

0 

Room 

_ _ 

V 

8 hours 

97° 

- - 

VI 

8 hours 

196° 

- - 

VII 

8 hours 

147° 

- - 

VIII 

8 hours 

147° 

Fe 

The 

temperatures  were 

maintained  by  hand 

regulation  of  the 

blast  lamp  and  varied 

within  three  degrees  during  the  ran,  the 

temperatures  given 

being  the  average  for 

the 

8 hours.  sample 

VIII  had  a staging  of  five  pieces  of 

iron  gauze  within  the 

inner  beaker,  with  iron  filings  of  about  30  to  40  mesh  sprinkled  on  the  gauze. 
Air  was  blown  through  this  and  stirring  and  heating  conducted  as  usual. 


5 

After  the  oxidizing  run  the  five  oil  samples  were  each  tested  for 
Flashpoint,  Fire  point.  Carbon  Residue,  Viscosity,  Specific  Gravity,  unsatura- 
tion, Capillary  rise,  Asphalt  Residue,  and  Total  Oxygen  by  combustion  method. 

In  all  the  tests  made  the  relative  rather  than  the  absolute  values  were 
most  desired.  Flash  and  Fire  were  determined  by  the  open  cup  method,  Specific 
Gravity  by  hydrometer.  Viscosity  in  seconds  (two  hundred  cu.  cm.)  with  an  Engler. 
Capillary  rise  was  determined  by  placing  a thermometer  stem  open  at  each  and  in 
the  oil  and  reading  the  rise  on  the  thermometer  scale.  Only  "soft'1  asphalt  resi- 
dues were  determined,  these  by  precipitation  in  petroleum  ether,  filtration,  solu- 
tion in  benzene  and  subsequent  evaporation  in  weighed  dishes,  unsaturation  was 
determined  by  the  method  of  Hubl1 using  a solution  of  25  gm.  of  iodine  and  30  gm. 
of  mercuric  chloride  in  500  cc.  of  95$  alcohol,  standardized  against  tenth  normal 
sodium  thiosulfate.  After  several  hours  digestion  potassium  iodide  solution  was 
added  and  the  remaining  iodine  titrated  using  starch  as  an  indicator.  The  results 
are  expressed  in  cubic  centimeters  of  iodine  solution  absorbed. 

For  determination  of  carbon  residue  a modification  of  Conradson’s  appa- 
ratus was  used  which  was  constructed  as  follows  (see  illustration).  A large  iron 
crucible  about  five  inches  in  diameter  was  set  into  a hole  in  a piece  of  asbestos 
board  about  a foot  in  diameter,  v/ithin  the  large  crucible  a smaller  iron  crucible 
was  set  on  a layer  of  sand.  Inside  of  the  small  iron  crucible  a porcelain  cruci- 
ble to  hold  the  oil  was  placed,  covers  were  fitted  to  both  of  the  iron  crucibles 
and  the  whole  apparatus  heated  by  a blast  lamp.  A bunsen  burner  flame  was  direct- 
ed toward  the  edge  of  the  outer  crucible  to  ignite  the  vapors  as  they  were  given 
off.  Heating  was  continued  at  a temperature  just  sufficient  to  produce  inflam- 
mable vapors  until  no  more  vapors  appeared.  Then  the  flame  was  turned  full  on  for 


five  minutes.  By  careful  regulation  of  the 

6 

rate  of  heating,  checks  on  the  deter- 

mination  to  within  one -tenth  of  one  percent 

were  easily  obtained. 

For  ready 

EXPERIMENTAL  ( MTA  ) . 
conparison  the  extensive  tables  of 

results  for  the  nine  de- 

terminations  on  five 

samples  of  the  oil  will  be  tabulated,  giving  here  only  the 

average  value  for  each  determination,  in  all  cases  duplicate  tests  were  made 

until  the  results  checked  within  the  limits 

of  error  of 

the  determination. 

Sample  Number 

Carbon  Residue 

Oxygen 

Asphalt  Residue 

$ 

$ 

% 

II 

.5(1) 

34 

.1(0) 

V 

.3(6) 

47 

.1(4) 

VI 

1.8(1) 

40 

.6(9) 

VII 

.8(1) 

5(?) 

.2(1) 

VIII 

.9(0) 

63 

.3(0) 

Sample  Number 

Flash  (C°) 

Fire  (C°) 

Nhsatu  ration 

' II 

213 

241 

c.c.  of  l2 
2.76 

V 

215 

246 

2.62 

VI 

217 

247 

2.51 

VII 

216 

246 

2.65 

VIII 

215 

245 

2.52 

Sample  Number 

Specific  Gravity  Capillary  Rise 

Viscosity 
(sec. 60°  C. ) 

II 

.863 

69.8 

196 

V 

.663 

68.3 

199 

VI 

.871 

67.4 

261 

VII 

.866 

69.0 

221 

VIII 

.867 

67.7 

225 

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VISCOSITIES 


Sample 

II 

V 

VI 

Temperature 

Time 

Temperature 

Time 

Terape  rature 

Time 

21.3 

1300 

25.0 

980 

28.0 

1420 

28.0 

765 

31.0 

700 

36.0 

895 

39.5 

455 

36.0 

537 

44.0 

520 

42.0 

405 

40- 

440 

50.0 

380 

59.0 

196 

48- 

308 

56.0 

297 

66.0 

163 

56.0 

225 

63- 

232 

78.2 

115 

68.0 

145 

77- 

147 

80.3 

110 

75.0 

130 

88 

115 

84.0 

105 

86- 

104 

93.0 

108 

99.0 

89 

96- 

92 

104.0 

93 

99.5 

87 

106.0 

83 

120.0 

75 

VII 

VIII 

Temperature 

Time 

Taupe rature 

Time 

28- 

897 

27.4 

953 

32- 

730 

33- 

722 

37.0 

558 

37- 

590 

43- 

426 

41.5 

464 

50- 

319 

47- 

365 

65.0 

182 

54.0 

277 

73.5 

146 

57.0 

241 

81 

118 

64- 

194 

91 

97 

72.0 

152 

100.0 

88 

81- 

122 

113.0 

78 

90- 

105 

100.0 

93 

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EXPERIMENTAL  (INTERPRETATION) 

Tlie  results  of  the  determinations  are  in  general  what  one  would  ex- 
pect from  the  conditions  of  the  run  on  the  oil  with  the  exception  of  Flash  and 
Fire  and  possibly  percent  of  oxygen. 

It  is  noticeable  that  the  effect  on  nearly  every  property  of  the  oil 
increases  with  the  increase  in  temperature.  The  maximum  change  in  every  value 
except  percent  of  oxygen  has  occurred  in  oil  Number  VI,  run  eight  hours  at  196° 

C.  Next  to  this  oil,  VIII,  run  eight  hours  at  147°  c.  in  the  presence  of  iron 
particles,  showed  the  greatest  change.  Then  come  in  descending  order  according 
to  magnitude  of  change, oils  VII  (eight  hours  147°  C.),  V (eight  hours  97°  c.), 

II  (fresh). 

Talcing  up  the  determinations  in  the  order  in  \diich  they  are  here  re- 
corded, one  first  considers  Carbon  Residue.  This  determination  is  relatively  new 
in  oil  analysis  and  while  its  exact  relation  to  lubricating  power  is  not  known, 
it  would  seem  to  be  a valuable  indication  of  the  stability  and  homogeneity  of  the 
constituents  of  the  oil.  The  work  on  the  oil  caused  a great  increase  in  the  Car- 
bon Residue,  and  it  is  logical  to  assume  that  the  lubricating  power  is  corres- 
pondingly low.  Asphalt  residue  shows  a similar  increase,  and  asphalt  residues 
are  not  lubricants.  The  presence  of  the  iron  filings  indicates  that  metallic 
particles  in  oil  may  catalyze  the  reaction  in  which  it  breaks  down.  Asphalt 
Residue  was  increased  almost  fifty  percent  due  only  to  the  iron,  and  Carbon  Res- 
idue shows  an  increase  in  the  same  pair  of  samples  which  can  only  be  due  to  the 
catalytic  effect  of  the  metal. 

The  test  for  unsaturation  is  distinctly  parallel  to  those  for  Carbon 
Residue  and  Asphalt  Residue,  particularly  the  latter.  This  is  logical  and  con- 


9 

firmatory  for  the  latter  tests  when  one  considers,  as  is  usually  done,  that 
asphalt  residues  are  the  direct  result  of  oxidation  and  polymerization  of  the  un- 
saturated hydrocarbons  in  the  oil. 

The  most  unaccountable  and  interesting  deviation  from  the  expected  ef- 
fect occurs  in  the  change  in  Plash  and  Fire  temperatures.  The  variation  in  aver- 
age temperature  between  the  different  samples  is  but  four  degrees  for  Flash  point 
and  six  for  Fire.  This  is  only  a little  more  than  the  possible  error  in  determi- 
nation by  the  method  used.  In  the  case  of  Sample  VI,  the  oil  was  maintained  at  a 
temperature  about  fifteen  degrees  below  its  Flash  point  with  a current  of  air 
passing  through  it,  for  eight  hours,  yet  it  lost,  apparently,  almost  none  of  the 
volatile  constituent  which  gave  the  observed  flash.  All  during  the  run,  however, 
vapors  were  visibly  given  off  from  the  oil,  and  especially  during  the  first  two 
or  three  hours.  It  may  be  that  the  fifteen  degree  difference  from  the  Flash 
Point  was  sufficient  to  protect  the  oil  from  loss  of  its  volatile  fraction,  but  i 
seems  logical  to  advance  another  explanation  for  the  appearance  of  the  ''flash'’. 
This  conclusion,  from  the  observed  behavior,  is  that  ’’flash”  and  ’’fire”  are  not 
due  to  simple  vaporization  of  the  lightest  constituents  of  the  oil,  but  are  due 
to  cracking  of  the  oil.  If  the  first  case  were  true  the  loss  of  vapors  during 
the  run  on  the  oil  should  have  made  a much  more  noticeable  difference  in  the 
Flash  and  Fire  Points.  Assuming  the  truth  of  the  latter  hypothesis,  one  immed- 
iately wonders  if  these  tests  (Flash  and  Fire)  may  not  indicate  something  of  more 
value  than  has  been  previously  supposed.  They  would,  it  seems,  indicate  not  only 
the  temperature  at  which  the  oil  begins  to  break  down,  but,  what  is  more  impor- 
tant, the  relative  stability  of  oils.  The  usual  test  might  well  be  modified  to 
consist  of  continued  heating,  when  an  increase  in  flash  temperature  would  dis- 


10 

tinguish  true  volatilization  of  an  oil  mixture  containing  various  fractions, 
from  the  cracking  at  constant  temperature  which  would  take  place  in  a better  oil 
of  more  uniform  composition.  In  this  way  an  accurate  idea  of  the  pureness  and 
homogeneity  of  the  oil  might  be  obtained. 

The  increase  in  Specific  Gravity  and  Viscosity  may  be  attributed  to 
the  same  reactions  of  oxidation  or  polymerization  or  both  which  formed  the  as- 
phalt residue  in  the  oil.  This  change  in  viscosity,  while  perfectly  definite, 
was  not  very  large.  In  special  cases  where  an  oil  of  very  definite  character 
should  be  used  the  change  in  lubricating  characteristics  due  to  its  viscosity 
might  be  objectionable,  but  in  ordinary  use  the  variation  is  too  slight  to  be 
noticeable,  in  internal  combustion  engines  burning  light  liquid  fuels  there  is 
almost  always  a mixing  of  the  fuel  with  the  oil  which  causes  a decrease  in  vis- 
cosity counteracting  the  increase  within  the  oil  itself. 

The  last  test  applied  was  decided  on  as  a possible  indication  of  that 
property  of  "oiliness",  the  simple  ability  to  prevent  friction  between  moving 
surfaces.  It  would  seem  that  surface  tension,  the  tendency  of  an  oil  to  remain 
in  contact  with  a surface  should  have  some  relation  to  the  property.  An  oil  of 
low  surface  tension  would  not  maintain  a film  on  the  face  of  the  bearing  as  well 
as  an  oil  of  high  surface  tension  when  subjected  to  the  mechanical  forces  and  the 
scraping  effects  in  the  bearing.  The  capillary  tube  used  gave  a rise  of  about 
four  centimeters  in  thirty  minutes.  This  time  was  chosen  as  being  sufficient  to 
permit  the  maximum  rise  with  the  tube  used,  for  after  that  period  of  time  no  ob- 
servable change  in  height  occurred  in  five  minutes.  With  smaller  tubes  the  rise 
and  also  the  differences  between  samples  were  greater,  but  the  effects  of  viscos- 
ity made  a determination  take  several  hours  and  the  temperature  and  hence  the  vis 


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cosity  would  change  before  all  the  samples  could  be  tested.  Granting  that  sur- 
face tension  is  one  indication  of  the  oil's  lubricating  power,  a definite  loss 
is  seen  in  the  oil  after  use. 

CONCLUSION. 

From  the  above  tests  one  may  draw  several  conclusions,  in  the  first 
place  atmospheric  oxidation  has  very  little  effect  on  a lubricating  oil  at  temp- 
eratures below  one  hundred  degrees,  for  Sample  V showed  only  slight  differences 
from  the  fresh  oil.  Using  the  same  amounts  of  air  though,  an  increase  in  heat 
of  fifty  degrees  in  samples  VI  and  VII  caused  a marked  change  in  the  oil,  and  one 
concludes  that  the  heating  effects  are  very  important.  An  oil  would  undoubtedly 
give  much  batter  service  if  it  could  ba  kept  cool  in  use.  The  catalytic  effect 
of  metallic  particles  is  vary  noticeable,  as  the  results  on  Samples  VII  and  VIII 
show,  in  all  probability  oxidation  effects  would  be  influenced  much  more  than 
other  effects  (as  polymerization)  by  the  metal,  so  one  may  conclude  that  the  air 
in  the  oil  plays  a definite  part  in  its  change.  Also  because  of  the  very  notice- 
able effect  of  the  metallic  particles,  a system  in  which  the  oil  is  used  and  re- 
used, returning  to  a reservoir  after  passing  through  the  bearings,  v/ould  preserve 
the  original  properties  of  the  oil  much  longer  if  a filter  were  installed  to  keep 
the  liquid  free  of  foreign  material. 


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12 


BIBLIOGEAPHY. 

1.  "Examination  of  Lubricating  Oils",  Stillman. 

2.  Bulletins  73  and  153,  Bureau  of  Standards. 

3.  Zaits.  Angew.  Chem.  (1891)  pg.  416-419. 

4.  Cbem.  Ztg.  (1895)  vol.  19,  pg.  41. 

5.  J.  Soc.  Cham.  Ind.  (1895)  vol.  14,  pg.  282. 

6.  J.  Soc.  Cham.  Ind.  (1892)  vol.  11,  pg.  619. 

7.  Bulletin  160,  Bureau  of  Standards. 


